Motor vehicle alignment systems are important for ensuring that the alignments of wheels on a vehicle are within the specifications provided by motor vehicle manufacturers. If the wheels are out of alignment, there may be excessive or uneven wear. In addition, the performance of the vehicle, particularly handling and stability, may be adversely affected if the wheels are not properly aligned. As used herein, the term “wheel” or “vehicle wheel” refers to the tire and wheel assembly found on a motor vehicle. Such an assembly generally includes a conventional tire that is mounted on a metal wheel or “rim.”
Many different types of apparatus have been developed to obtain balancing information for a wheel. One balancing apparatus currently in use involves mounting a wheel on a spindle. The spindle and wheel are then rotated, and forces generated by the wheel are measured to obtain such information as tire and/or rim lateral and radial runout and improper bead seating of the tire on the rim.
The balancing apparatus also simulates a road test by applying a radial force or load to the wheel while the wheel is rotating. From the simulated road test, a measure of tire uniformity is obtained. Tire uniformity is the change in the sidewall and footprint as the force is exerted against the tire. In a current system, a roller having a diameter approximately one-sixth the diameter of the wheel is being used to exert the radial force against the wheel. Because the roller has such a small diameter, the force being exerted by the roller against the wheel is distributed over a considerably smaller footprint than if the force was being exerted by ground against the wheel.
In the above-described balancing apparatus, the spindle is typically located greater than one wheel diameter above the surface upon which balancing apparatus is positioned. As such, a technician using the balancing apparatus is required to lift the wheel a considerable distance to mount the wheel on the spindle. This lifting and subsequent lowering of the wheel can be particularly burdensome, as certain wheels, for example for SUVs, weigh in excess of ninety pounds. There is, therefore, a need for an improved balancing apparatus that reduces the lifting required by a technician to mount the wheel on the balancing apparatus, and a balancing apparatus that better simulates road conditions during testing.